Position location for mobile devices can provide various services. For example, retailers can offer a higher level of customized services such as concierge services or promotions tailored to the user's profile and history with the retailer if the users opt to share their accurate location within the store. Similarly, public venues such as airports and museums can efficiently deliver higher level of services if they have the knowledge of where their users are within the venue in a timelier and more context aware manner. For example, an airport venue may provide accurate estimates of time to the gate incorporating real-time assessment of security checkpoints. The airport venue could provide reminders of flight boarding if a user is far away from their gate before boarding time (e.g., taking into account the user's current location and estimated time to make it back to the gate). Additionally the airport venue could suggest suitable outlets nearby if a user is unfamiliar with the area (e.g., saving time to find their preferred brand of coffee or pizza). There are many possible use cases for various levels of position accuracy (e.g., city block level, 50 m, 10 m, 5 m, etc.).
Conventional position location techniques based upon signals provided by Satellite Positioning Systems and/or cellular base stations may encounter difficulties when a mobile device is operating within a building and/or within urban environments. In such situations, signal reflection and refraction, multipath, and/or signal attenuation can significantly reduce position accuracy, and can slow the “time-to-fix” to unacceptably long time periods. These shortcomings may be overcome by having the mobile device exploit signals from network based positioning (NBP), such as Wi-Fi (e.g., IEEE 802.11x standards), to derive position information. Conventional NBP techniques may utilize round trip time (RTT) measurements derived from signals utilized within a network of wireless access points. A wireless access point (AP) can be a device that allows wireless devices to connect to a wired network using Wi-Fi, or other wireless standards.
Utilizing NBP measurement techniques to determine position typically involves requesting positioning information from nearby APs of the mobile device. A limitation of NBP systems is in the allocation and management of limited wireless bandwidth. For example, multiple mobile devices simultaneously requesting positioning information from an AP may saturate the limited bandwidth of the AP. If the AP schedules measurement requests for all the requests simultaneously, the AP will be overloaded with measurement requests and cannot take measurements for all the devices. Furthermore, collision probability will be high. Multiple simultaneous positioning requests will also result in high NBP load (e.g., NBP load associated with servicing network positioning or location requests), creating inefficiencies. If all the requests are scheduled sequentially, then the AP may not be able to process every request. High traffic areas such as malls may benefit from NBP but may also be susceptible to network overload. Additionally, APs generally will set aside a smaller percentage of overall network bandwidth for positioning, and instead allocate most bandwidth to data connections. There is a need for a NBP system that is able to efficiently allocate network bandwidth.